It was demonstrated that the same mosaic membrane may be selectively anion permeable for transport processes and selectively cation permeable for electrical processes. This was accomplished by using a mosaic membrane consisting of a high resistance (275,000 omega) liquid anion exchanging membrane in parallel with a fairly high resistance (9,580 omega) porous cation exchanging membrane. When this mosaic membrane separated .05 N RbSCN from .1 N RbSCN, a concentration potential resulted with the more dilute side positive. This indicated that the membrane was more electrically permeable to cations than anions. The self-exchange transport rates as determined with radioactive isotopes showed, however, that the thiocyanate anion was transported over 400 times faster than the rubidium cation across the membrane. The main reason for this apparent conflict is that the anions were transported across the membrane in an essentially undissociated form. Their rate was not dependent upon the electrical potential of the mosaic membrane nor upon the electrical resistance of the liquid anion permeable membrane part. The demonstration is of value in understanding that similar processes may be working in the much more complex biological membrane systems.